Okay so ultimate branding is a GREAT plugin, but in the spirit of WPMUdev's desire for continuous improvement, I have a few feature suggestions that I think will make Ultimate Branding an EXCELLENT plugin.
1) More Admin Bar Customization- As of now, the customization allowed for the Admin Bar is only really for functionality. Besides the logo, there isn't a way to really brand the look and feel of the admin bar.It would be really nice to be able to change the colors, fonts, and even size of the admin bar.
2) Admin Menu Customization- Besides removing the permalinks menu, I'm not aware of any other customization that is allowed for the admin menu in Ultimate Branding. I've been using this plugin here: http://wordpress.org/extend/plugins/admin-menu-editor/ It's really great for hiding menus, reordering menus, changing menu names, changing menu icons, and even adding new menu links. It even has a very easy to use drag and drop UI. I think adding something VERY similar to Ultimate Branding would increase the value by quite a lot.
3) Custom Dashboard- I love that Ultimate Branding let's me hide all the Dashboard clutter as well as create my own Dashboard Widget. However, it would be really great if we could FULLY customize the Dashboard by changing the background colors and basically create a fully custom startpage for users.
Those are my thoughts! I love this plugin, and I know WPMUdev will only make it better!